Integrated circuits are interconnected networks of electrical components fabricated on a common foundation called a substrate. The electrical components are typically fabricated on a wafer of semiconductor material that serves as a substrate. Various fabrication techniques, such as layering, doping, masking, and etching, are used to build millions of resistors, transistors, and other electrical components on the wafer. The components are then interconnected (e.g., wired together) to define a specific electrical circuit, such as a processor or a memory device.
Flash memory devices are one particular class of memory devices that have developed into a popular source of non-volatile memory for a wide range of electronic applications. Non-volatile memory is memory that can retain its data values for some extended period without the application of power. Flash memory devices typically use a one-transistor memory cell that allows for high memory densities, high reliability, and low power consumption. Changes in threshold voltage of the cells, through programming of a charge storage node, such as a floating gate or charge trap, or other physical phenomena, determine the data value of each cell. By defining two or more ranges of threshold voltages to correspond to individual data values, one or more bits of information may be stored on each cell. Common uses for flash memory and other non-volatile memory include personal computers, personal digital assistants (PDAs), digital cameras, digital media players, digital recorders, games, appliances, vehicles, wireless devices, mobile telephones and removable memory modules, and the uses for non-volatile memory continue to expand.
Multi-level memory, e.g., those defining three or more ranges of threshold voltages are increasing in interest. One way to facilitate defining additional ranges of threshold voltages is to increase the usable threshold voltage range of the memory cells. This generally results in a need to use increasing voltage levels on control gates of these memory cells. Traditional field-effect transistors present a challenge to operate effectively in providing these increasing voltage levels.
For the reasons stated above, and for other reasons which will become apparent to those skilled in the art upon reading and understanding the present specification, there is a need in the art for alternative transistor configurations.